5,353 research outputs found
Isocausal spacetimes may have different causal boundaries
We construct an example which shows that two isocausal spacetimes, in the
sense introduced by Garc\'ia-Parrado and Senovilla, may have c-boundaries which
are not equal (more precisely, not equivalent, as no bijection between the
completions can preserve all the binary relations induced by causality). This
example also suggests that isocausality can be useful for the understanding and
computation of the c-boundary.Comment: Minor modifications, including the title, which matches now with the
published version. 12 pages, 3 figure
On General Plane Fronted Waves. Geodesics
A general class of Lorentzian metrics, , , with any Riemannian manifold, is introduced in order to generalize classical exact plane fronted waves. Here, we start a systematic study of their main geodesic properties: geodesic completeness, geodesic connectedness and multiplicity, causal character of connecting geodesics. These results are independent of the possibility of a full integration of geodesic equations. Variational and geometrical techniques are applied systematically. In particular, we prove that the asymptotic behavior of with at infinity determines many properties of geodesics. Essentially, a subquadratic growth of ensures geodesic completeness and connectedness, while the critical situation appears when behaves in some direction as , as in the classical model of exact gravitational wave
Computability of the causal boundary by using isocausality
Recently, a new viewpoint on the classical c-boundary in Mathematical
Relativity has been developed, the relations of this boundary with the
conformal one and other classical boundaries have been analyzed, and its
computation in some classes of spacetimes, as the standard stationary ones, has
been carried out.
In the present paper, we consider the notion of isocausality given by
Garc\'ia-Parrado and Senovilla, and introduce a framework to carry out
isocausal comparisons with standard stationary spacetimes. As a consequence,
the qualitative behavior of the c-boundary (at the three levels: point set,
chronology and topology) of a wide class of spacetimes, is obtained.Comment: 44 pages, 5 Figures, latex. Version with minor changes and the
inclusion of Figure
Further properties of causal relationship: causal structure stability, new criteria for isocausality and counterexamples
Recently ({\em Class. Quant. Grav.} {\bf 20} 625-664) the concept of {\em
causal mapping} between spacetimes --essentially equivalent in this context to
the {\em chronological map} one in abstract chronological spaces--, and the
related notion of {\em causal structure}, have been introduced as new tools to
study causality in Lorentzian geometry. In the present paper, these tools are
further developed in several directions such as: (i) causal mappings --and,
thus, abstract chronological ones-- do not preserve two levels of the standard
hierarchy of causality conditions (however, they preserve the remaining levels
as shown in the above reference), (ii) even though global hyperbolicity is a
stable property (in the set of all time-oriented Lorentzian metrics on a fixed
manifold), the causal structure of a globally hyperbolic spacetime can be
unstable against perturbations; in fact, we show that the causal structures of
Minkowski and Einstein static spacetimes remain stable, whereas that of de
Sitter becomes unstable, (iii) general criteria allow us to discriminate
different causal structures in some general spacetimes (e.g. globally
hyperbolic, stationary standard); in particular, there are infinitely many
different globally hyperbolic causal structures (and thus, different conformal
ones) on , (iv) plane waves with the same number of positive eigenvalues
in the frequency matrix share the same causal structure and, thus, they have
equal causal extensions and causal boundaries.Comment: 33 pages, 9 figures, final version (the paper title has been
changed). To appear in Classical and Quantum Gravit
A proteomic approach to study the low temperature stress induction in bell pepper fruit
Comunicaciones a congreso
A proteomics study of chilling injury in tomato fruit, a low-temperature stress-induced physiological disorder affecting fruit quality
Trabajo presentado a la conferencia "Molecular Basis of Plant Stress" celebrado en Bulgaria del 21 al 23 de septiembre de 2011.-- FP7 REGPOT Project "BioSupport".Tomato (Solanum lycopersicum L.) is the second most cultivated horticultural crop in the world in terms of harvested area and production, after the potato (FAOSTAT 2011, data from 2009). A main problem regarding its postharvest life is its sensitivity to low temperature stress during refrigerated storage, which constitutes a main obstacle for its long-term commercialization. This sensitivity is reflected in the physiopathy of chilling injury (CI), which negatively affects the final fruit quality. The main symptoms of CI-affected fruits are skin depressions, tissue decomposition and impaired ripening, which results in deficient flavour and aroma. Physiological and biochemical events involved in CI progress have been extensively described, but the precise molecular mechanisms that ultimately regulate the plant response to cold stress remain unclear. In order to investigate this response at molecular level in tomato fruit a proteomics strategy has undertaken. The proteome analysis provides a direct insight on the changes undergone by proteins, which are the major functional determinants of the cell machinery, in a certain biological situation such as low temperature stress. The protein expression profile of chilled tomato fruits has been compared with fruits stored at nonchilling temperature (control). The protein analysis has been performed by two-dimensional differential-in-gel-electrophoresis (2D-DIGE), and mass spectrometry of protein spots was applied to identify proteins differentially expressed. Comparative analysis revealed significant changes in abundance of 31 identified proteins between the proteomes of chilled and control fruits. Major modifications in the expression profile are related to those proteins specifically involved in stress (chaperonins and heat-shock proteins); cell wall biochemistry (hydrolytic enzymes), and carbohydrate metabolism (enzymes involved in glycolisis, tricarboxylic acids cycle, photosynthesis and sucrose biosynthesis).This work was supported by the Spanish Ministry of Science and Innovation (MICINN) through grant and PIE2009-40I080, and by the Council of Science and Technology from the Spanish Region of Murcia (Fundación SENECA) through grant no. 04553/GERM/06.Peer Reviewe
La promoción de salud en la comunidad
En el presente trabajo se analiza el papel que desempeñan las universidades en la transformación y el desarrollo social, con énfasis en el rol de la extensión universitaria como núcleo clave y expresión de su pertinencia, también se estudia el impacto social en la comunidad. La extensión universitaria es una de las vías en donde la Universidad demuestra su carácter de centro cultural significativo para el desarrollo. En el trabajo se valora su importancia en la sociedad, definiciones del concepto de extensión universitaria, se analizan conceptos directamente relacionados con la temática de manera determinante
Fat-specific FUS-DDIT3-transgenic mice establish PPARgamma inactivation is required to liposarcoma development.
Peer reviewe
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